Excessive sodium can be linked to blood pressure issues and fluid retention. Some people are more prone than others to problems. Personally, I have to be very careful with my salt/sodium intake for two reasons - family history of heart problems, and I will retain lots of fluid (will even have pitting edema).
Most people, however, don't need to worry too much unless you are at risk for heart problems. Chances are pretty good that if you are eating healthy whole foods, minimal amounts of processed or restaurant foods, and are mindful of added salts/seasonings, you shouldn't really have anything to worry about.
A lot of the time, people who consume a lot of sodium aren't eating very well to begin with, in which case, they have several things to worry about, not just salt intake.
I believe the RDA is 2400mg/day, and the average is somewhere over 3000, but I could be getting my numbers wrong.